Diffuse idiopathic skeletal hyperostosis (DISH) has been reported as a risk factor for revision surgery after posterior decompression or decompression with fusion for lumbar spinal stenosis. Although ankylosis extending into the lumbar segments (L-DISH) has been associated with poor outcomes, evidence regarding mid- to long-term outcomes after fusion surgery in patients with DISH remains limited. This study evaluated clinical outcomes and revision rates following posterior lumbar interbody fusion (PLIF) for lumbar degenerative spondylolisthesis in patients with DISH who were followed for more than 5 years postoperatively.

We retrospectively reviewed 321 consecutive patients who underwent 1- or 2-level PLIF for lumbar degenerative spondylolisthesis. Patients were classified into DISH (D) and non-DISH (N) groups according to the Resnick criteria and Mata grading system. Demographic data, preoperative and postoperative visual analog scale (VAS) scores and Japanese Orthopaedic Association Back Pain Evaluation Questionnaire (JOABPEQ) domain scores, and revision rates were compared between groups.

A total of 100 patients (25 in the D group and 75 in the N group; mean age 66.5 years; mean follow-up

8.1 years) were included. Among the 25 patients in the D group, 8 had L-DISH, whereas the remaining cases had thoracic-limited DISH (T-DISH). Baseline characteristics were comparable between groups. Postoperative VAS scores for all symptoms significantly improved in both groups; however, postoperative lower-extremity numbness VAS scores were significantly higher in the D group (D: 4.3 vs. N: 2.5, P = 0.039). Regarding JOABPEQ, the effective rate for walking ability was significantly lower in the D group (D: 52.0% vs. N: 74.3%, P = 0.037). The overall revision rate was significantly higher in the D group (D: 28.0%, N: 10.7%, P = 0.042). Within the D group, revision rates were 24% in T-DISH cases and 38% in L-DISH cases. The mean interval from the initial surgery to revision surgery was 3.7 years in L-DISH cases and 5.6 years in T-DISH cases, with revisions occurring later in T-DISH.

With postoperative follow-up exceeding 5 years, increased revision rates became evident even in patients with thoracic-limited DISH. Preoperative assessment of thoracic DISH may therefore be crucial when planning PLIF for lumbar degenerative spondylolisthesis.